1. The Field of the Invention
The present invention relates to human/computer interface input devices, and, more particularly, to computer input devices for simulating medical procedures.
2. The Relevant Art
Virtual reality computer systems provide users with the illusion that they are part of a "virtual" environment. A virtual reality system will typically include a computer processor, such as a personal computer or workstation, specialized virtual reality software, and virtual reality I/O devices such as head mounted displays, pointer gloves, three-dimensional ("3D") pointers and the like. Virtual reality computer systems have been used successfully for training in many fields, such as aviation and vehicle and systems operation. The appeal of using virtual reality computer systems for training relates in part to the ability of such systems to allow neophyte practitioners the luxury of operating in a highly realistic environment and making disastrous mistakes without consequence to the trainee, others or property. Thus, for example, a trainee pilot or automobile driver can learn to fly (or drive) using a virtual reality simulator without concern for accidents that would cause death and/or property damage in the real world. Similarly, operators of complex systems, e.g., nuclear power plants and weapons systems, can safely practice a wide variety of training scenarios that would risk life or property if performed in reality.
The advantages of simulation have not gone unnoticed in the medical field, which has become increasingly concerned with the costs of malpractice and inefficient care management. For example, a virtual reality computer system can allow a doctor-trainee or other human operator or user to "manipulate" a scalpel or probe within a computer-simulated "body", and thereby perform medical procedures on a virtual patient. In this instance, an I/O device as a scalpel or probe. As the "scalpel" or "probe" moves within the body, an image is displayed on the screen of the computer system, and the results of the pointer's movements are updated and displayed so that the operator can gain the experience of performing such a procedure without practicing on an actual human being or a cadaver.
For virtual reality systems to provide a realistic (and therefore effective) experience for the user, sensory feedback and manual interaction should be as natural as possible. As virtual reality systems become more powerful and as the number of potential applications increases, there is a growing need for specific human/computer interface devices which allow users to interface with computer simulations with tools that realistically emulate the activities being represented within the virtual simulation. Such procedures as laparoscopic surgery, catheter insertion, and epidural analgesia should be realistically simulated with suitable human/computer interface devices if the doctor is to be properly trained.
While the state of the art in virtual simulation and medical imaging provides a rich and realistic visual feedback, there is a great need for new human/computer interface tools which allow users to perform natural manual interactions with the computer simulation. For medical simulation, there is a strong need to provide doctors with a realistic mechanism for performing the manual activities associated with medical procedures while allowing a computer to accurately keep track of their actions. In addition to tracking a user's manual acivity and feeding such information to the controlling computer to provide a 3D visual represtation to the user, a human interface mechanism should also provide force feedback to the user, so the user can obtain realistic tactile information as well. Thus an effective human interface not only acts as an input device for tracking motion, but also as an output device for producing realistic tactile (haptic) sensations.
There are number of devices that are commercially available for interfacing a human with a computer for virtual reality simulations. There are, for example, such 2-dimensional input devices such as mice, trackballs, and digitizing tablets. However, 2-dimensional input devices tend to be awkward and inadequate to the task of interfacing with 3-dimensional virtual reality simulations. In contrast, a 3-dimensional human/computer interface tool, sold under the trademark Immersion PROBE.TM. is marketed by Immersion Human Interface Corporation of Palo Alto, Calif., allows manual control in 3-dimensional virtual reality computer environments. A pen-like stylus allows for dexterous 3-dimensional manipulation, and the position and orientation of the stylus is communicated to a host computer. The Immersion PROBE has six degrees of freedom which convey spatial coordinates (x, y, z) and orientation (role, pitch, yaw) of the stylus to the host computer.
While the Immersion PROBE is an excellent 3-dimensional interface tool, it may be inappropriate for certain virtual reality simulation applications. For example, in some of the aforementioned medical simulations three or four degrees of freedom for a 3-dimensional human/computer interface tool is sufficient and, often, more desirable than five or six degrees of freedom because it more accurately mimics the real-life constraints of the actual medical procedure.
The application of virtual reality simulation to the operation of catheters, and other elongated flexible objects, often require only two, three or four degrees of freedom. In particular, catheters work in a largely two dimensional environment created by the channel into which the catheter is inserted, e.g., a vein or artery. The forces to which a catheter is subjected often are simplified compared to other medical implements, consisting mainly of drag forces. Therefore, a less complex virtual reality device is desirable for certain applications.